Thermosolutal and Soret-driven convection of power-law fluids in an inclined horizontal cavity

Abstract

The interaction among thermal buoyancy, solutal effects, and non-Newtonian rheology in inclined enclosures is important for predicting heat and mass transfer in double-diffusive convection systems. This study compares double-diffusive and Soret-induced convection in an inclined cavity filled with a non-Newtonian power-law fluid and examines the effect of cavity inclination on both configurations. A horizontal heat flux is applied to the vertical walls, while the top and bottom walls are impermeable and thermally insulated. Solutal gradients are generated either by imposing constant concentration gradients on the vertical sidewalls or through the Soret effect. The problem is solved using a combined analytical and numerical approach, where the analytical formulation is based on the parallel-flow approximation and the numerical solution is obtained from the two-dimensional governing equations. The results show that cavity orientation strongly affects flow intensity and heat and mass transfer, with maximum transfer rates obtained when the cavity is heated from below. For the double-diffusive case, the strongest convective response occurs at inclination angles of −80°, −60°, and −50° for power-law indices of 0.6, 1.0, and 1.4, respectively. At θ = −80°, increasing the power-law index from 0.6 to 1.4 reduces the maximum stream function, Nusselt number, and Sherwood number by approximately 87%, 93%, and 97%, respectively. The Soret-induced case shows similar stream-function and Nusselt-number trends, but marked differences in Sherwood-number behavior. The novelty lies in directly comparing both solutal mechanisms under identical physical conditions.